package com.project.m.api.busi.util;

import java.security.MessageDigest;

public class MD5Util {

    private static final String hexDigits[] = {"0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

    private static String byteArrayToHexString(byte b[]) {
        StringBuffer resultSb = new StringBuffer();
        for (int i = 0; i < b.length; i++)
            resultSb.append(byteToHexString(b[i]));

        return resultSb.toString();
    }

    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0)
            n += 256;
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

    public static String MD5Encode(String origin, String charsetname) {
        String resultString = null;
        try {
            resultString = new String(origin);
            MessageDigest md = MessageDigest.getInstance("MD5");
            if (charsetname == null || "".equals(charsetname))
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes()));
            else
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes(charsetname)));
        } catch (Exception exception) {
        }
        return resultString;
    }

    public static byte[] MD5Encode(byte[] origin) {
        byte[] result = null;
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            result = md.digest(origin);
        } catch (Exception exception) {
        }
        return result;
    }

    /**
     * 计算字符数组特定部分的MD5值.
     *
     * @param info  字符数组
     * @param start 字符数组开始计算的下标
     * @param len   字符长度
     * @return md5值
     */
    public static String getMd5(byte[] info, int start, int len) {
        try {
            byte[] temp = new byte[len];
            System.arraycopy(info, start, temp, 0, len);
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] digest = md.digest(temp);
            StringBuffer hexString = new StringBuffer();
            for (int i = 0; i < digest.length; i++) {
                if ((0xff & digest[i]) < 0x10) {
                    hexString.append("0" + Integer.toHexString((0xFF & digest[i])));
                } else {
                    hexString.append(Integer.toHexString(0xFF & digest[i]));
                }
            }
            return hexString.toString();
        } catch (Exception ex) {
            return null;
        }
    }

}
